Role of rice volatiles in the foraging behaviour of the predator Cyrtorhinus lividipennis for the rice brown planthopper Nilaparvata lugens

Experiments were conducted in laboratory to study the impacts of rice genotypes and rice plants treated with different levels of nitrogen on the predation rates of the predator, Cyrtorhinus lividipennis Reuter, for eggs of the rice brown planthopper (BPH), Nilaparvata lugens (Stal), and their relation to the rice volatiles. In two-choice test, the predator females showed different predation rates for BPH eggs on different rice genotypes, but not for BPH eggs on rice plants treated with different levels of nitrogen. The olfactory response test revealed that more female predators oriented to the odours from healthy rice plants compared with the plain air (control); the predator preferred plant-BPH nymph complex over healthy plants, and plant-BPH gravid female complex over plant-BPH nymph complex. Additional experiments demostrated that there were obvious differences in attractiveness of the healthy plants and plant-BPH gravid female complex of various rice genotypes, while no significant differences were found between rice plants treated with different levels of nitrogen. The results of predation rates of the predator on various varieties and plants treated with different levels of nitrogen were consistent with that of its olfactory response in 5 of the 6 cases evaluated, which showed that rice volatiles played an important role in the foraging behaviour of C. lividipennis. Implications for augmenting the effectiveness of natural enemies by adjusting rice attributes and cultural practices are discussed.